Incandescent lamp



July 29, 1952 P.O.CARTUN INCANDESCENT LAMP Filed June 1, 1951 hWVTWtOT. Paul, O. Cav tun, y W /K% His Atlqovne3 Patented July 29, 1952 1 2,605,446- INCANDESCENT LAMP 7 Paul 0. Cal-tun, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Application June 1, 1951, Serial n 229,372

My invention relates to electric incandescent lamps which are adapted to be operated in series;

and more particularly to a lamp of suchtype having means associated therewith for indicating a breakage or failure of the filament within the lamp. Certain types of electric incandescent lamps,- such'for example as those employed for Christmas tree lighting and which may be termed miniaturelamps, are operated by connecting a given number of the lamps in series whereby the combined voltages of the several lamps equal the line voltage supplying the'electrical energy. However, when used in such manner, considerable inconvenience occurs upona failure of one of the lamps, as for instance when a filament breaks or burns out, since such failure interrupts the continuity ofthe circuit andthe rest of the lamps in the circuit are extinguished. When a string or plurality of series-connected lamps become thus. extinguished because of such failure it .is difficult to determine which lamp i'adefective. In order to discover the lamp which has failed it becomes necessary to separately test each lamp of the series until the defective lamp is found. This procedure involves considerable time and inconvenience and has heretofore caused considerable annoyance in connection with series-burning lamps. I

It isan object of. the present invention, there fore, to provide an electric incandescent lamp operable to give a positivevis'iblev indication of afailure in the filament of a lamp.

Another object of the invention is to provide an electric incandescent lamp operable to energize an auxiliary filament therein and simultaneously'form a coating on the lamp envelope whichimparts a distinctive appearance to the lamp upon failure of the main filament.

' Still another object of the'invention is to provide an electric incandescent lamp having an auxiliary filament therein which is automatically connected into the lamp circuit upon failure of the main filament and the energization of which causes the deposition of a substantially light-im- 'pervious coating on the inner surface of the lamp envelope.

In "accordance with the invention, an incandescent lamp for series operation is provided with main and auxiliary filaments'shunted at one end by a normally insulative cut-out or shunt which,..upon failure of the main filament,'be.- comes conductive and operative to connect the auxiliary filament into the lamp circuit. Thev auxiliary filament of the lamp is provided, in ad- 4 Claims. a (01; 315-120) dition, witha quantity of a readily vaporizable material which, upon 'energization and-heating of the auxiliary filament,- is vaporized off the filament and is flashed or deposited onto the'interior surfaceof. the envelope to form a distinc-' ti've coating. Preferably; the said vaporizable material is'a'metal, such as magnesium for example, which forms a substantially light-impervious coating on the envelope'which prevents transmission of the light from the auxiliary filament and thus gives to .the lamp a darkened or unlighted appearance providing a visible indication that the lamp is defective or burned out.

Further objects and advantages of my invention will appear from the following detailed description of species thereof and 'from theac companying drawing in which:

Fig. l is a=longitudinal 'sectionoi an electric incandescent lamp according to 'theinvention; Fig. 2 isan elevation of a modified form of lamp according to the invention, and Fig. 3 is an elevation of another modification. I

' Referring'toFig. 1 of the drawings, the invention'is there shown as applied to 'an electric incandescent lamp of' the double-ended type comprising a sealed elongated glass envelope or bulb I provided at its ends with base members 2 and3 and having a pair of filaments 4 and 5 mounted therein constituting, respectively, main and auxiliary filaments. In the particular case illustrated, the main and auxiliary filaments 4, 5 are constituted by a single length of tungsten or other suitable filament wire provided with coiled portions or segments which form the main and auxiliary filaments 4,5 and which are joined by an intermediate bight portion 6. The vtwo filaments 4, 5 may, however, be formed as entirely separate members, if desired. The auxiliary or secondary filament 5 may be of'substantially the same resistance as the main or primary filament 4.- In the form of the invention shown in Fig. 1, the two filament portions 4, 5 extendalongside one another in a direction more orlesslengthwise'of the elongated envelope l. The filaments 4, Sam supported in place by relatively rigid lead-in conductors or' wires 1 and 8 sealed through the opposite ends of the envelope and electrically connected, respectively, to the bases 2 and3. Conductor. I is connected to the intermediate or filament bight portion 6 joining themain and auxiliary filament portions 4 and 5 at one end thereof, while lead-in conductor 8 is connected to the other end of the main filament portion 4. The other or free end of the auxiliary filament portion 5 is con- 'i t ff 7 2,605,446

, i 3 nected to a relatively rigid dummy current conductor 9 which extends alongside the lead-in conductor 8 and is supported in place therefrom by a cut-out or shunt member IIJ which bridges and ties together the two conductors 8, 9. 5 The cut-out or shunt I0 is of a type Which is normally non-conductive when the normal voltage of the singleflampt'i's applied zthereacross' but which becomes conductive when a higher voltage is applied to it such as occurs when the main fila- 1c ment 4 becomes broken or otherwise fails. The" particular cut-out I0 illustrated comprises ia pairof closely spaced beads H, I2 of suitable insulat ing material, such as powdered. silica or-.-gla'ss; fusion-sealed around and bridgingthe conduc l5 tors 8, 9 and having the space between the beads filled with a suitable cut-out material l3-so as to surround and bridge the said conductors 8, 9. V The cut-out or shunt material l3 may 'l'oe,"for instance, of the type described and claimed in 2) U.-.S. Patent,l,992,844,; Severin et al., andcomprising gamixture' of a metalpowderf-suchas-ironpowder, a finely: powdered; insulating material such as, cryolite'; powder; andja binider suehwas sodium silicate; Under ordinary operatin condi: tionsthe sodium silicategand: cryoliteHg-ive the mixture insulating properties, but-upon failure of the main filamentcflof the lamp when-connected inser-ies the increase in voltage across'thelamp terminals is such that the resistanceof ,thecutout is insumcient to prevent;the-current frompassing' from one'conductor fi' to the other con-- ductorlm In a preferred form of the invention,--the-auxiliaryfilament 5 is provided with aycoatingl l of a readily vaporizable material, such as magnesium or aluminum for example, whichisvaporized or fiashed ofi the filament upon" energization'a'nd resultant heating thereof. and which will-.thendeposit on the envelope wall in sufiicient quantityrto' 9 form: a substantialy; 1 light-impervious lor opaque coating thereon. The coating i4--'ma-yz conveniently be in the former a bead'constituted-of a paste made from fine magnesium-powder; mixed with and held t'ogetherzbya suitable binder such. as nitrocellulose; dissolved in 1 amyl acetate; for example.:"fl It will be obvious'that the:vaporizablermaterial 14, instead of being one which producesian'opaque coating; maybe a material such as lead'joxide or cadmium-sulphidelw-hich produce a colored; diffusing or other distinctivecoating; I

'In the normal seriesoperation of. the lamp according to the invention; the normal operating voltage-of the-single lampds applied-to'the cut- 50 outor shunt 10; However; since-the cut-out or; shunt I0 is non-conductiveatsuch normal operating:voltage.or the-lamp,-;the-current will therefore pass through: thezmaim filament 4- only. Upona failure of. the mainfilament-A, however; the full line'voltage applied across all :the" lamps in the series is then applied across'the conductors 8, '9 and-to the cut-out material l3therebetween; causingia break-down of theinsulatingoxide or dielectric in the cut-out material 1 3 which thereforerr'enders the latter conductive? and: permits the'passage of current between conductors 8 and. 9 arid consequently a flow of current throrugh'the auxiliary filament 5 as well'as through'the'remaining lamps in theseries; The resultingienergization and-heating of theauxiliary filament 5' vaporizes the magnesium or other vaporizable metalconta'in'ed in the coating'or bead 'l l' there-"- on, which vaporized metal then condenses on the inner surface of the envelope wall inform a sub'-' 4 stantially light-impervious or opaque coating thereon. The resulting absorption or obstruction by such coating of the light from the energized auxiliary filament 5 gives the lamp a darkened appearance which clearly distinguishes it from the other operating lamps in the series by reason of their normal lighted appearance, and which therefore provides a ready -visibleindication of the particular lamp in the series which has failed.

The modification shown in Fig. 2 diners from the construction shown in Fig. l principally in that itemploys a simplified form of filament construction wherein the main and auxiliary filament portions .4.,.,-5, together with their interconnecting straight bight portion 6', are arranged in a-substantially straight line extending diagonally to the longitudinal axis of the envelope I, with the intermediate bight portion 6' located substantially in the said axis where it is clamped or otherwise connected to the lead-in conductor]; The opposite endsot the filament 4', 5i are Jconnected;respectively;v to the conductors'B! an'dfiflas beforei Y Fig. 3fillustrates. the application of the invention vto a lamp of' a single-ended typesuch as is generally used for Christmas tree lighting and comprising a sealed glass envelope. [-5 provided witha single neck end intowhich amount'lfi is butt-sealed. The mount 16 comprises lead-in wires or conductors 1" or 8" which-are-butt sealed through the neck end-of'the envelopeand are connected to the terminals, e. 'gf, the-base shell [8 and eyelet IQ; of a conventional base-H suitably fastened to the neck 'en'd of theenvelope, as by basing cementfor'in'stance. A dummy conductor 9" extends alongside the lead-in con ducto'r 8? and is suppcrte'dith'erefrom in nor mally ihsulatedrelation by'tlfie normallyfnonconductive cut-out'or shunt m which may beef the-sameconstruction as that shown in Figs-l and 2fand which bridges the .two conductors 8.", 9" but does not'contact the other ,conductor'l". The three conductors 1", Bf' 'and 9" supporir'a V'-sha'ped filament comprised of coiledmain and auxiliary leg portions 4" and 5", respectively,

joined at the apex of the filament by a connect.- ing bight portion 6. Conductor 'l is corrnected to the intermediate bight portion 6's of the filament while conductors 8 and9 are connected to the free. ends of; the coiledfmain and auxiliary filament portions 4" and 5", respec tively. The coiled auxiliary filament portion 5"j is provided with a coating, or bead I 4 of a readily vaporizable metal such as magnesium, the same asinFigs.1and2.f Y

As in the c'aseof the lamps of Figs. l and 2,1the normally non-conductive cut-out ll) of the lamp shown in Big. 3 becomesconductivelupon failure of .the main filament 4" and thus connects the auxiliary filament 5" into the lamp-circuit. The resulting energization and heatingof the auxiliary filament 5 then vaporizes the magnesium or other vaporizable metal in the bead M to forma light-impervious coating on' the envelopewall normally lighted lamps in the series-and indi catingit as a defective lamp.

Although: preferred species" of my inventionhave been disclos'edit will be understood thatthe' invention is not to be'limited to thespecific: constriictions and arrangements 'of parts'shown, but: that they may be-Widely' modified withinj'thespirit and scope of my invention as defined by the appended claims. e

What I claim as new and desire to secure by Letters Patent of the United States is: v

1. An electric incandescent lamp comprising a sealed envelope, a main filament and an auxiliary filament in said envelope electrically interconnected at one of their respective ends, a pair of lead-in wires sealed through said envelope, one of said lead-in wires being electrically connected to the said interconnected ends of said filaments and the other of said lead-in wires being 816C? trically connected to the other end of said main filament, an electrical conductor connected to the other end of said auxiliary filament, a cut-outbridging the said other lead-in wire and the said electrical conductor, said cut-out being non-con: Y

ductive when the normal operating voltage of the lamp is applied thereto but becoming conductive when a higher voltage is applied to it, and a quantity of a readily vaporizable material on said auxiliary filament adapted to be vaporized therefrom onto the envelope upon energization of said auxiliary filament.

2. An electric incandescent lamp comprising a sealed envelope, a filament in said envelope, a pair of lead-in wires sealed through said envelope, one of said lead-in wires being electrically connected to an intermediate point of said filament and the other of said lead-in wires being electrically connected to one end of said filament, an electrical conductor connected to the other end of said filament, a cut-out bridging the said other lead-in wire and the said electrical conductor, said cut-out being non-conductive when the normal operating voltage of the lamp is applied 7 thereto but becoming conductive when a higher voltage is applied to it, and a quantity of a readily vaporizable material on the portion of said filament connected to said electrical conductor and adapted to be vaporized therefrom onto the envelope upon energization of the said portion of the filament.

3. An electric incandescent lamp comprising a sealed envelope, a filament in said envelope comprising a main portion and an auxiliary portion joined by a bight portion, a pair of lead-in wires sealed through said envelope, one of said lead-in wires being electrically connected to said bight portion and the other of said lead-in wires being electrically connected to the free end of said main filament portion, an electrical conductor electrically connected to the free end of said auxiliary filament portion, a cut-out bridging the said onto the envelope upon energization of the said auxiliary filament portion.

4. An electric incandescent lamp as set forth in claim 1 wherein the said vaporizable material comprises a bead of magnesium.

PAUL QcARTUN.

No references cited. 

